Injection moulding machines and moulds are commercially available for the production of injection moulded plastic articles. During the moulding cycle, molten plastic is injected in the cavities of the mould and usually the mould, which is cooled by circulating chilled water, remains closed until the injected article is sufficiently cold to be ejected from the mould and is free dropped by gravity.
When the walls of the moulded article are thick, more cooling time is required, making the cycle time longer and reducing production output. To overcome this problem, systems are available where the mould opens before the article is fully cooled and is ejected into a robot arm, which takes the warm article to be cooled further outside the mould (post cooling), either in one or more post cooling stations beside the injection moulding machine or in the robot arm itself, which then has cooling means incorporated. In this way the mould can open sooner to save cycle time, however there is substantial cost in providing a robot with fast movements and complex cooling means. Such methods of post cooling are the most widely used and a particular version is covered in CN101072667 (HUSKY). Although providing for good post cooling, the method involves very costly robotic and handling equipment.
In other existing methods of providing post cooling, instead of being ejected onto a robot arm, the articles remain on the cores (male parts) of the injection mould for one or more extra cycles. In such cases two or more sets of cores must be provided, together with a mechanism to move each set of cores alternately between injection position and post cooling positions. Such methods make the cost of the injection mould much more expensive, because of the duplication of cores and other mould parts, including separate means of ejecting the articles.
An attempt to use vertical rather than horizontal post cooling positions, in order to take advantage of the force of gravity to keep the articles in contact with the cooling surfaces of post cooling positions is described in JP2000289098 (NISSEI). In this case however, a non-standard injection moulding machine is used, with a vertical clamping unit instead of the usual horizontal clamping. Furthermore, complex handling equipment is required.